The present invention relates to a mechanically controllable valve lift adjustment. The present invention also relates to an internal combustion engine having a mechanically controllable valve lift adjustment and to a method of controlling the valve lift in internal combustion engines.
In internal combustion engines, when changing from full load to partial load, a negative pressure occurs in the suction unit, causing more fuel than required to be drawn into the cylinders. As a result, the fuel consumption of the internal combustion engine is increased, and unburned fuel is possibly released into the environment.
The object therefore is to provide a device by means of which the fuel consumption in an internal combustion engine can be reduced.
Said object is accomplished by providing a mechanically controllable valve lift adjustment for an internal combustion engine having multiple cylinders, including:
at least one lifting lever per cylinder, which has
a means bearing the lifting lever rotatably and displaceably in a connecting member,
a drive transmission means cooperating with a camshaft driving the lifting lever, and
a working curve,
a means which cooperates with the displaceable, rotatable bearing of the lifting levers, displacing the latter in the connecting members,
a camshaft which cooperates with the drive transmission means of the lifting lever and drives the latter,
at least one valve per cylinder, which cooperates with the working curve of one lifting lever at a time, being moved by same,
the means displacing the lifting lever being a driven rail held displaceably in a bearing in the housing of the internal combustion engine.
In another embodiment, the valve lift adjusting means according to the invention additionally has a roll drag lever which, on the one hand, cooperates with the working curve of the lifting lever, being driven by same, and, on the other hand, cooperates with the valve and moves the latter.
According to the invention, the valve lift adjusting means has a means bearing the lifting lever rotatably and displaceably in a connecting member. Said means preferably is a roll.
The connecting member receives said means, thus representing a guide thereof, wherein said meansxe2x80x94and the lifting lever at the same timexe2x80x94is displaced under pressure and/or traction. The connecting member can be of any shape, the shape being selected by a person skilled in the art in such a way that the lifting lever preferably can be displaced along a particular straight line and/or curve.
However, the connecting member preferably is of an essentially rectangular shape, the short sides of the rectangle preferably being designed so as to take the shape of a semicircle. Such a shape of the connecting member is particularly suited to receive rolls. The connecting member can be arranged horizontally or vertically, or at any angle with respect to the horizontal and/or vertical.
According to the invention, the internal combustion engine has at least two cylinders, each cylinder being associated with at least one lifting lever. By means of a driven rail held displaceably in a bearing in the housing of the internal combustion engine, the position of the lifting levers is changed so as to adjust the cylinder lift. Preferably, the rail is moved back and forth along a straight line.
In a preferred embodiment of the present invention, one cylinder has two intake valves and accordingly, two lifting levers. According to the invention, these two lifting levers can be displaced either by one driven rail or by two driven rails, and in this latter case, one lifting lever is displaced by one rail at a time. This latter embodiment is advantageous in that the lifting levers and thus, the valves, can be adjusted independently, allowing an even more variable control of the internal combustion engine. In extreme cases, a so-called zero lift is implemented on one valve, while the other valve is completely opened.
The rail can be driven in any way known to those skilled in the art. For example, the drive is by hydraulic or pneumatic means using an electric lifting magnet, an electric motor preferably having a transmission, or a piezo motor.
Preferably, the means cooperating with the camshaft is a roll.
The valve control of the invention is suitable for valves of any type. However, the valves preferably are valves of internal combustion engines, more preferably intake valves of internal combustion engines.
Therefore, the present invention is also directed to an internal combustion engine having at least one valve control according to the invention.
Furthermore, the present invention is directed to a method of controlling the intake valve lift of an internal combustion engine using the valve control according to the invention, wherein at least two lifting levers are displaced in the connecting member by a driven rail in accordance with the requirements as to the performance of the internal combustion engine.
Under partial load, the lifting lever is displaced in such a wayxe2x80x94and maintained in this position for some timexe2x80x94that the valve or the roll drag lever makes contact with that part of the working curve of the lifting lever which provides a reduced valve lift.
Under full load, the lifting lever is displaced in such a wayxe2x80x94and maintained in this position for some timexe2x80x94that the valve or the roll drag lever makes contact with that part of the working curve of the lifting lever which provides maximum valve lift.
The present invention is advantageous in that the valve lift can be increased or reduced depending on the performance required. The valve lift adjustment according to the invention reduces the load alternation work in Otto engines, resulting in fuel savings of up to 10% compared to prior art valve control. The production of a mechanical control is substantially easier and thus, more cost-effective compared to e.g. an electronic valve lift control. The valve control according to the invention is very robust and insensitive in terms of maintenance. By using a rail displacing the position of the lifting levers, the number of component parts required is substantially less compared to the prior art.